Whilst as a moderator I should not be pushing you away, I have to say that this is probably not the right place to ask. Firstly the PA32 is relatively rare in the UK. There are only 87 registered and most will be retractable types. You would be better asking on one of the social media forums that include American owners and a more targeted membership.
That said. Essentially you're really just dealing with a PA28 with another row of seats. Structurally there won't be much more to maintain. The main costs differences will be in prop overhauls, fuel consumption and insurance. The other thing to remember is that with AVGAS on its way out there is a remote possibility that should supplies dry up your engine may not be eligible to run on UL91. If that happens you're looking at owning a hangar Queen until the matter is resolved.
Field performance will be similar due to the excess power available, but of course that will be tempered by load.
If you want to gauge insurance then use Visicovers website and get a quote just to get a feel and work on more detailed quotes once you're likely to move on one.
This page seems to offer some figures:
PA32-300 Specs